1. Field of the Invention
The present invention relates generally to cleaning contaminants such as oil and grease from the surface of substrates such as metal and plastic parts using a biological cleaning system which cleans the parts and digests the contaminants so that the cleaning solution is maintained in an active state over an extended cleaning time period and, in particular, to the use of a combination cleaning and treating bath and/or a recycle pre-treatment and/or post-treatment bath to provide an efficient and cost effective integrated biological cleaning system.
2. Description of Related Art
While microorganisms have been used for many years to digest oil from wastes and spills, the integration of biodegradation with aqueous cleaning for metal and other material finishing applications is a relatively recent process. Mild alkaline emulsifying cleaners that operate at relatively low temperatures are now used to integrate the removal of oil and particulates in a parts cleaning operation with biological digestion of the residues. The system is essentially self-regulating, since the microbial activity will adjust itself to the amount of removed oil and grease present in the system.
In a typical system used in the metal finishing industry, an alkaline cleaning solution and control system is employed that utilizes microbes in the solution to consume the oil/grease that is removed from parts during the cleaning process. The system operates at relatively low temperatures (104xc2x0 F.-131xc2x0 F.) (40xc2x0 C.-55xc2x0 C.) and a pH range of 8.8-9.2, which is a viable habitat for the microorganisms. The cleaning process actually takes place in two separate operations. When parts come in contact with the solution, the oil and impurities are emulsified into micro-particulates. The micro-particulates are then consumed by microorganisms which are present in the bath. The microbe consumption of the oil present in the bath, as its food source, results in the production of CO2 as a by-product. The microbes are naturally present in industrial oils and greases, and the main species responsible for biodegradation has been identified as pseudomonas stutzeri, a microorganism found in soil and water.
In one process operation, the cleaning solution from a cleaning tank is pumped continuously between a separator module and the cleaning tank. This operation is run in a continuous mode without interruptions for solution dumping and new solution make-up. As a result of the dynamics of the process and the re-circulation of the bath solution, the consumption of oil by the microbes occurs throughout the biological degreasing system. For an efficient operation the oil must be emulsified and oil must be present at all times to keep an active population of microorganisms. In the case of a longer interruption that may be conducive to the total depletion of the oil present in the system, to keep the microbes alive it is necessary to render them dormant typically by increasing the pH to 10.5 or alternatively, to feed them with small amounts of oil during the down time.
The typical system is managed by a control unit which controls the process parameters such as temperature and pH, and the replenishment of surfactants and nutrients, maintaining the chemical and biological equilibrium. It is possible to operate the system without downtime for extended periods (up to many years), eliminating the need of dumping spent cleaning solutions. The enhanced productivity and the reduced use of chemicals and water have made the system well suited to fulfill the present needs of the industry.
Biological cleaning systems offer many advantages over conventional chemical cleaners. The life of the cleaning solutions have been lengthened to the point that today there are many operations where the original cleaning solution is in use many years after installation. Biological cleaning process also creates practically no solid or liquid waste that requires treatment and disposal. The degreasing processes are also more effective since the parts are treated with a cleaning solution that is continuously rejuvenated and always has about the same composition and a consistent oil removal ability. Biological cleaning systems offer major economies savings in chemicals, labor, waste disposal and energy costs.
The biological cleaning systems used today have been adapted to the requirements of a broad range of industrial applications, and currently the process is used in electroplating, painting, powder coating anodizing and general metal and plastic working operations.
While biological cleaning has proven its effectiveness in a large number of installations, under certain conditions the parts to be cleaned must be pre or post treated and/or are not totally cleaned since contaminants still remain on the surface. This requires further steps to specially treat or clean the part which affects the cost effectiveness of the total part treating process. One particular application is the need to provide a clean, phosphated part for further processing, such as painting. This process now requires a number of non-integrated steps. In another application, parts which have been cleaned or partially cleaned in a biological cleaner are now post-treated by electrocleaning in an electrocleaner bath. This process likewise now requires a number of non-integrated steps.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a method for cleaning substrate surfaces in which the parts are cleaned to commercial standards and which substrates may also be pre or post treated, i.e., phosphated, electrocleaned, etc. for further downstream processing.
It is another object of the present invention to provide a biological cleaning system for cleaning substrate surfaces which provides parts cleaned to commercial standards and which parts may also be pre or post treated, i.e., phosphated, electrocleaned, etc. for further downstream operations.
In another object of the present invention a method and apparatus are provided for providing cleaned, treated parts in a single step cleaning and treating bath such as a detergent phosphating bath, which bath may be used with or without the pre- or post-treatment steps described above.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The above and other objects, which will be apparent to those skilled in art, are achieved in the present invention which is directed to a method for cleaning and/or treating substrate surfaces comprising the steps of:
providing a biological cleaning bath comprising a surfactant for cleaning and emulsifying oils and/or greases on a substrate surface and microbes for digesting the emulsified oils and/or greases;
providing a pre-treatment bath for pre-treating the substrate to be cleaned, the pre-treatment bath comprising a composition which is biologically compatible with the cleaning bath;
immersing the substrate to be cleaned in the pre-treatment bath for a sufficient time to pre-treat the substrate;
removing the pre-treated substrate from the pre-treatment bath and immersing the pre-treated substrate in the biological cleaning bath for a sufficient time to clean the substrate;
removing the biologically clean substrate from the biological cleaning bath;
periodically or continuously removing a portion of the pre-treatment bath and adding the removed portion to the biological cleaning bath where the components of the bath are digested by the microbes;
replenishing the pre-treatment bath; and
continuing the above steps until the desired number of substrates are cleaned.
In another aspect of the invention a method is provided for cleaning and/or treating substrate surfaces comprising the steps of:
providing a biological cleaning bath comprising a surfactant for cleaning and emulsifying oils and/or greases on a substrate surface and microbes for digesting the emulsified oils and/or greases;
providing a post-treatment bath for post-treating the substrate to be cleaned, the post-treatment bath comprising a composition which is biologically compatible with the cleaning bath;
immersing the substrate to be cleaned in the biological cleaning bath for a sufficient time to clean the substrate;
removing the cleaned substrate from the biological cleaning bath and immersing the cleaned substrate in the post-treatment bath for a sufficient time to post-treat the substrate;
removing the post-treated substrate from the post-treatment bath;
periodically or continuously removing a portion of the post-treatment bath and adding the removed portion to the biological cleaning bath;
replenishing the post-treatment bath; and
continuing the above steps until the desired number of substrates are cleaned and post treated.
In an additional aspect of the invention a method is provided for cleaning and/or treating substrate surfaces comprising the steps of:
providing a biological cleaning bath comprising a surfactant for cleaning and emulsifying oils and/or greases on a substrate surface and microbes for digesting the emulsified oils and/or greases;
providing a pre-treatment bath for pre-treating the substrate to be cleaned and a post-treatment bath for post treating the cleaned substrate, the pre-treatment bath and post-treatment each comprising a composition which is compatible with the cleaning bath;
immersing the substrate to be cleaned in the pre-treatment bath for a sufficient time to pre-treat the substrate;
removing the pre-treated substrate from the pre-treatment bath and immersing the pre-treated substrate in the biological cleaning bath for a sufficient time to clean the substrate;
removing the biologically clean substrate from the biological cleaning bath;
immersing the cleaned substrate in the post-treatment bath for a sufficient time to post-treat the substrate;
removing the post-treated substrate from the post-treatment bath;
periodically or continuously removing a portion of the pre-treatment bath and post-treatment bath and adding the removed portions to the biological cleaning bath;
replenishing the pre-treatment bath and post-treatment bath; and continuing the above steps until the desired number of substrates are pre-treated, cleaned and post-treated.
In a further aspect of the invention a method is provided for cleaning and treating substrate surfaces comprising the steps of:
providing a biological cleaning and treating bath comprising a surfactant for cleaning and emulsifying oils and/or greases on a substrate surface, microbes for digesting the emulsified oils and/or greases and a compatible treatment composition such as an iron phosphating composition;
immersing the substrate to be cleaned and treated in the biological cleaning and treating bath for a sufficient time to clean and treat the substrate;
removing the cleaned and treated substrate from the biological cleaning and treating bath;
continuing the above steps until the desired number of substrates are cleaned and treated.
In a further aspect of the invention a biological cleaning system is provided comprising:
a tank containing a biological cleaning bath comprising a surfactant for cleaning and emulsifying oils and/or greases on a substrate surface and microbes for digesting the emulsified oils and/or greases;
a tank containing a pre-treatment bath for pre-treating the substrate to be cleaned, the pre-treatment bath comprising a composition which is compatible with the cleaning bath;
means for transferring a portion of the pre-treatment bath from the pre-treatment tank to the biological cleaning tank;
means for replenishing the pre-treatment bath;
wherein substrates to be cleaned are immersed in the pre-treatment bath for a sufficient time to pre-treat the substrate and then removed from the pre-treatment bath and immersed in the biological cleaning bath for a sufficient time to clean the substrate and a portion of the pre-treatment bath is removed either periodically or continuously and transferred to the biological cleaning bath where contaminants in the transferred pre-treatment bath are digested by the microbes.
In an additional aspect of the invention a biological cleaning system is provided comprising:
a tank containing a biological cleaning bath comprising a surfactant for cleaning and emulsifying oils and/or greases on a substrate surface and microbes for digesting the emulsified oils and/or greases;
a tank containing a pre-treatment bath, the pre-treatment bath comprising a composition which is compatible with the cleaning bath;
a tank containing a post-treatment bath for post-treating a cleaned substrate, the post-treatment bath comprising a composition which is compatible with the cleaning bath;
means for transferring part of the pre-treatment bath from the pre-treatment tank to the biological cleaning tank;
means for transferring a portion of the post-treatment bath from the post-treatment tank to the biological cleaning tank;
means for replenishing both the pre-treatment bath and the post-treatment bath;
wherein substrates to be cleaned and post-treated are immersed in the pre-treatment bath to pre-treat the substrate, the pre-treated substrate then being immersed in the cleaning bath to clean the substrate and then immersed in the post-treatment bath to post-treat the substrate and periodically or continuously removing a portion of the pre-treatment and post-treatment bath and transferring the removed portions to the biological cleaning bath where contaminants in the pre-treatment bath and post-treatment bath are digested and replenishing the pre-treatment bath and post-treatment bath as needed.
In a further aspect of the invention a biological cleaning system is provided comprising:
a tank containing a biological cleaning bath comprising a surfactant for cleaning and emulsifying oils and/or greases on a substrate surface and microbes for digesting the emulsified oils and/or greases;
a tank containing a post-treatment bath for post-treating a cleaned substrate, the post-treatment bath comprising a composition which is compatible with the cleaning bath;
means for transferring a portion of the post-treatment bath from the post-treatment tank to a biological cleaning tank;
means for replenishing the post-treatment bath;
wherein a substrate to be post-treated is immersed in the biological cleaning bath for a sufficient time to clean the substrate and then removed and immersed in the post-treatment bath for a sufficient time for post-treating the substrate and a portion of the post-treatment bath is periodically or continuously removed from the post-treatment tank and added to the biological cleaning tank where contaminants in the post-treatment bath are digested and the post-treatment bath is replenished as needed.
In another aspect of the invention a biological cleaning and treating system is provided comprising:
a tank containing a biological cleaning and treating bath comprising a surfactant for cleaning and emulsifying oils and/or greases on a substrate surface, microbes for digesting the emulsified oils and/or greases and a compatible treating composition such as an iron phosphating composition;
wherein a substrate to be cleaned and treated is immersed in the biological cleaning and treating bath for a sufficient time to clean and treat the substrate and then removed.